If “The Passage,” by Pen/Hemingway Award-winner Justin Cronin, does only half as well as his publishers are hoping and the book world is expecting, the mainstream writer and his neo-vampire trilogy-in-the- making will be the envy of genre writers and the obsession of vampire- fiction-loving fans the world over.

Cronin, who already has scored $3.75 million from publishers and another $1.75 million from blockbuster Hollywood director Ridley Scott for the movie rights, has said he wrote the book mainly because his daughter, 8 years old at the time, asked him to write a book about a little girl who saves the world. Request granted.

Owing a debt, and paying homage, to such classics as “Earth Abides” and Stephen King’s “The Stand,” Cronin’s apocalyptic thriller hits all the right notes. Unlike the recent spate of zombie fiction (such as “Pride, Prejudice and Zombies,” little more than the literary equivalent of sampling) — “The Passage” will likely join King’s end-of-the-world opus and books like Robert McCammon’s “Swan Song” in the pantheon of genre classics.

Although “The Passage” is the first of three books, Cronin gets everything right the first time out: suspenseful pacing, using third-person viewpoints that alternate throughout his massive tome (766 pages, 2.4 pounds), interesting, semi-formulaic characters with all-too human flaws (from a pedophile laborer and a misunderstood prisoner, to a motherly African nun and an FBI agent with a powerful paternal instinct), and just enough verisimilitude in his SF-cum-horror plot to have readers believing the fictional apocalypse in his story just might be plausible.

After a brief, 16-page introduction to the character of Amy Bellafonte, Cronin sends his narrative into overdrive as the next two chapters let the reader in on all the basics. A virus discovered in South American jungles is being used for experiments by the military (death-row prisoners, naturally, are the test subjects).

It’s not giving anything away to say that plans go awry, subjects escape and infect others, and soon an end-of-the-world scenario is playing out as those who are infected — called virals — hunt down those who are not.

The virals are a cross between vampires, zombies, killer apes and aliens, with exoskeletons that glow in the dark. And they move as fast as cheetahs.

Amy, abandoned at a convent early in the book, soon hooks up with Wolgast, an FBI agent whose daughter died years before. Like the original test subjects, Amy has psychic abilities.

An early scene in which she first communes with caged polar bears and then drives the entire zoo population crazy is done particularly well. And Amy appears in the dreams of many people, leading to the belief that she might be the one person who can save what is left of the human race.

Yes, there are moments when the book might read like a pastiche of other classics of the apocalyptic subgenre, but it is obvious there is a bit of homage at work.

And while Cronin is sure- handed in the chapters that delve into each character’s motivations and background, he is equally masterful in the action set-pieces, keeping the narrative speeding forward like a runaway train.

Even with its heft, “The Passage” is never dull. Nearly every chapter increases the narrative momentum, and readers will find themselves hard-pressed not to stay up for a 24- or 48-hour marathon reading session.

“The Passage” is certainly the first serious contender of the 21st century worthy of sitting alongside apocalyptic/ post-apocalyptic fiction classics like “The Stand,” “On the Beach” and “Earth Abides.”

And Cronin nails the ending, leaving readers with just the right sort of tease to keep them waiting on the edges of their seats for the promised sequel in two years.

Many people feel this will be the “it” book of the summer; there’s little reason to disagree.

If there’s one superhero character whose rise might be most tied to the events of World War II, it is Captain America, who emerged from the minds of legends Joe Simon and Jack Kirby and sprung forth from an iconic 1941 debut cover on which Cap smacks Hitler right in the kisser.